net: netsec: Fix signedness bug in netsec_probe()

The "priv->phy_interface" variable is an enum and in this context GCC
will treat it as an unsigned int so the error handling is never
triggered.

Fixes: 533dd11a ("net: socionext: Add Synquacer NetSec driver")
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/socionext/netsec.c

@@ -2007,7 +2007,7 @@ static int netsec_probe(struct platform_device *pdev)
 			   NETIF_MSG_LINK | NETIF_MSG_PROBE;
 
 	priv->phy_interface = device_get_phy_mode(&pdev->dev);
-	if (priv->phy_interface < 0) {
+	if ((int)priv->phy_interface < 0) {
 		dev_err(&pdev->dev, "missing required property 'phy-mode'\n");
 		ret = -ENODEV;
 		goto free_ndev;